Antioxidant



o-dianisidine,

dine, tetramethyl-benzidine, etc. All of these Patented Apr. 14, 1931 UNITED STATES PATENT 1' LUDWIG J. GHRISTMANN, or JERSEY CITY, NEW :rEnsEY, AssIeNoB. To AMERIGAlN CYANAMID COMPANY, on NEW YORK, N. Y., A coRPonA'rIoNoF-MAINE nnrroxinnn'r J No Drawing.

This invention relates to compounds for retardmg or preventing the oxldation of orgame substances, and compositions containing the same. Such antioxidants have many p R R R Ill, 7 was in which R represents hydrogen or alkyl groups, atleast one B standing for an alkyl radical. It is understood that the term alkyl group or radical refers not only to'a hydrocarbon residue containing carbon and hydrogen but is also meant to include a radical or group containing other elements in addition to those mentioned.

, More specifically, among the compounds falling within this class may be mentioned o-tolidine, tetraethyl-benzisubstances have been successfully used and have been found to retard or entirely pre vent deterioration of organic compounds such as rubber, due to oxidation. The antioxidants described maybe prepared in any manner well known to the art, the following specific example of a method suitable for the preparation of tetramethylbenzidine being given purely by Way of illus tration and not in limitation:

A mixture of parts dimethyl aniline, 260 parts sulphuric acid (90%), and 2 parts turpentine, is heated for about four hours in an oil bath maintained at a temperature of 190-200 C. The reaction mixture is cooled by being'poured on ice, and after cooling is neturalized with ammonia, filtered Application filed August 21,1928. Serial No. 301,159.

and the solids washed with water. 'The crude product remainingonthe filter may then be recrystallized from toluol. By this method the yield of crude productiss'ubstantially quantitative. v

To illustrate the effectiveness of this antioxidant, a standard vulcanizable rubber mixture was made up containing about 1%, by weight, of tetramethyl-benzidine. 'The mixture was then vulcanized at 288 F. for thirty minutes and cut up into test pieces.

A break test was carried out on several test pieces and others of the test pieces were placed in an oxygen bomb which was maintained at C. for three days under an oxygen pressure of 300 pounds. This test was devised to permit a rapid determination of the effect of oxygen upon the rubber, the results corresponding approximately to what might be expected to take place in a much greater period of time in ordinary use of the rubber composition. The following table illustrates the effect of the presence of the' small amount of antioxidant:

Tension atbreak s.sq'.1n.

Before After aging aging 7 Rubber compound with 1% tetramethyl-benndine 2870 2380 A similar rubber composition made up and vulcanrzed under the same conditions, but contaimng no antioxidant, was found to deteriorate completely after the same acceler- 2. A rubber composition containing tetramethyl benzidine.

3. The process of retarding oxidation of an oxidizable organic compound which comprises mixing therewith a tetra alkyl substituted-benzidine. V. V r v a 4:. The process of retarding oxidation of an oxidizable organic compound which comprises mixing therewith tetramethyl benzidine." I

5. The processof retarding oxidation of a rubber composition which comprises mixing a tetra alkyl substituted" benZidinetherewith. n

6. The process of retarding oxidation of a rubber composition which comprises mixingtetramethyl benzidine therewith.

In testimony vwhereof, I haye hereunto subscribed my name this 15 day of August,

1928. I v V r LUDWIG J. GHRISTMANN. 

